The present invention relates to a dressing for use in negative-pressure wound therapy, more particularly for wounds in the abdominal region, comprising a flexible film as a wound contact layer and at least one conduit applied to the film, wherein there can be a fluid-conducting connection between the conduit and the wound space through openings in the conduit and in the film.
Apparatus for negative-pressure wound therapy are known in the prior art. For instance, WO 1993/009727 describes an apparatus for promoting wound healing by the application of negative pressure on the area of skin including the wound and surrounding the wound. The apparatus according to WO 1993/009727 comprises vacuum means for creating the negative pressure, an air-tight wound covering referred to as sealing means, which is operatively associated with the vacuum means, and a wound dressing referred to as screen means for positioning on the wound within the sealing means. The screen means is a porous polymer foam material, for example a polyester foam. According to the description of WO 1993/009727, the use of negative-pressure therapy can speed up wound healing of different types of wounds, such as, for example, burn wounds, pressure sores or lacerations.
Large-area wounds in particular can occur in the abdominal region either as a result of injuries or as a result of surgical procedures. Surgical procedures in the abdominal region are, for example, performed in the surgical treatment of acute and life-threatening diseases of the abdominal cavity. In the context of postoperative care of such surgical procedures, there may also be the need to cover only temporarily the open abdominal region by means of a temporary covering.
WO 01/85248 discloses a dressing for the temporary covering of wounds resulting from accidents or surgical procedures, more particularly abdominal wounds. The dressing is intended for use in negative-pressure therapy. WO 01/85248 proposes covering the floor of the wound with a film provided with holes. A porous foam is applied to the film, which represents the wound contact layer. On the side facing away from the wound, the dressing comprises a liquid-impermeable film drape having an adhesive edge for air-tight closure of the wound area. In addition, connection means are provided, which extend through the film drape up to the porous foam, so that the wound space can be connected with a negative-pressure source. During operation, wound exudate can be removed from the wound space, with the liquid reaching, through the openings of the perforated film, first the porous foam and further on, via the foam, the connection means, which is in direct contact with the porous foam.
WO 01/85248 aims in particular for a temporary wound closure which can be changed without injuries owing to covering the floor of the wound with the dressing. Injuries during change of dressing are avoided according to WO 01/85248 by reducing the direct contact of porous material with the floor of the wound.
According to one embodiment of WO 01/85248, the dressing comprises one or more further layers of porous foam material, wherein the foam layer on the wound side is surrounded on all sides by the film provided with holes.
An abdominal wound dressing having a structure according to WO 01/85248 is commercially available under the name V.A.C.® “Abdominal™ Dressing Kit” (KCI).
Foam layers surrounded by a closed envelope cannot be cut to the size of the wound, since the envelope would otherwise be destroyed.
US 2009/0099519 describes an abdominal dressing for negative-pressure therapy, comprising a heating element for temperature control. In addition, the dressing can likewise comprise a foam layer (pad) surrounded by a closed envelope, wherein the thus encapsulated foam layer can be in direct contact with the wound.
A foam layer applied to the wound contact layer, as described in WO01/85248 for example, is, when using the apparatus as a temporary wound closure, in direct contact with the wound edges, since these are not sutured or closed during the duration of the temporary opening. The contact between foam layer and wound edges has an advantageous effect on the growth of the wound edges and therefore facilitates the primary wound closure when the wound is finally closed after it has been kept open temporarily.
However, in the case of an apparatus as described in WO 01/85248, i.e., in the case of an abdominal wound dressing comprising not only a film provided with holes as a wound contact layer but also a foam layer, any contact between the foam layer and the floor of the wound (i.e., exposed organs or omentum majus) must be avoided as far as possible in order to avoid the foam and the exposed organs or omentum majus sticking together or growing together. Contact between the foam layer and the floor of the wound through the openings of the film must therefore likewise be avoided. The wound contact layer applied between the porous foam and the floor of the wound therefore ought to have, according to WO 01/85248, openings which constitute less than 10% of the area of the film, more particularly only 1-2% of the area or less. According to WO 01/85248, the openings in the film can also be present in the form of slits, which further reduces contact between the foam and the floor of the wound.
However, a reduction in the area of the openings in the film serving as a wound contact layer can lead to reduced permeability to wound fluid, and so the removal of exudate from the wound space to the foam layer might be impeded.
During the duration of application of an abdominal wound dressing, more particularly when using an abdominal wound dressing as a temporary wound closure, it may be necessary to drain a very large amount of liquid, for example more than 5 liters within 48 hours. There may be very large amounts of liquid to be drained during, for example, the surgical treatment of an intestinal obstruction (ileus) or a peritoneal inflammation (peritonitis). In the case of the abdominal wound dressings known from the prior art, comprising a combination of a film provided with holes and a foam layer, the open area of the openings may, as described above, be limiting for the removal of the exudate. Furthermore, the fluid permeability of the foam layer may also be limiting for the removal of the exudate: the fluid permeability of the foam layer may be reduced owing to compression which occurs during application of negative pressure and which leads to a reduction in the pore volumes of the foam. In addition, during the duration of use, the fluid conductibility of the foam may be further impaired by clumping caused by exudate constituents.
In the case of abdominal wound dressings which are currently commercially available, the foam layer is typically smaller than the film provided with openings, and so although the foam layer covers the central surface area of the film, it does not cover the edge area of the film. Typically, the foam layer, provided it is a foam layer which can be adjusted in size, is adjusted in shape to the wound edges, and so the foam layer is in contact with the wound edges, while an edge area of the film provided with openings is carefully inserted between the inner organs and the abdominal wall. When inserting the film provided with openings between the inner organs and the abdominal wall, this must be done very carefully so as not to injure the inner organs. Since no cavity is present in the space formed by the inner organs and the abdominal wall, fluid cannot be removed via the edge area of the film provided with openings inserted under the abdominal wall. For the draining of wound exudate, therefore, only the foam layer-covered area of the film provided with openings is available.